1. Field of the Invention
The present invention relates to a light emission device and a display device using the light emission device as a light source. More particularly, the present invention relates to an electron emission unit in a light emission device and that emits electrons toward a phosphor layer.
2. Description of the Related Art
There are many different types of light emission devices that radiate visible light. Some light emission devices include an anode electrode and a phosphor layer on a front substrate and an electron emission region and driving electrodes on a rear substrate. The front and rear substrates are sealed to each other at their peripheries using a sealing member and the inner space between the front and rear substrates is exhausted to form a vacuum panel.
The driving electrodes include cathode electrodes and gate electrodes above the cathode electrodes in a direction crossing the cathode electrodes with an insulation layer therebetween. An opening is formed in the gate electrode and the insulation layer at each crossing area of the cathode electrodes and the gate electrodes, and an electron emission region is on a corresponding cathode electrode in the opening of the insulation layer. The driving electrodes and the electron emission regions form an electron emission unit.
When a predetermined driving voltage is applied to the cathode electrodes and the gate electrodes, an electric field is formed around the electron emission region by the voltage difference between the two electrodes. As a result, electrons are emitted from the electron emission region. The emitted electrons are attracted to a high voltage applied to the anode electrode, collide with the phosphor layer, and excite the phosphor layer to emit visible light.
The electron emission unit having the above-described structure is typically manufactured by repeating a thin film process and a thick film process several times. A well-known manufacturing method for the electron emission unit includes: (i) forming cathode electrodes by coating a metal layer on a rear substrate through a thin film process such as sputtering or vacuum deposition and patterning the metal layer; (ii) forming an insulation layer by repeating screen printing, drying, and baking an insulating material several times; (iii) forming gate electrodes by coating a metal layer on the insulation layer again through a thin film process and patterning the metal layer; (iv) forming an opening by wet-etching a predetermined part of the gate electrodes and the insulation layer; and (v) forming electron emission regions by screen-printing, drying, and baking a paste mixture having electron emission materials inside the insulation layer opening and activating the surface thereof.
As described above, the method for manufacturing the electron emission unit becomes very complicated. Since it is important to align a member formed in a current process with members formed in previous processes, additional efforts are required to check the alignment of the members. Therefore, a large amount of time and cost are required for manufacturing the conventional electron emission unit.
Also, some electrons collide with a side wall of an insulating layer opening so as to apply an electric charge thereto, because an initial angle spread of an electron beam is comparatively large when an electron emission region emits electrons in the electron emission unit. The resulting electric charge at the insulation layer lowers withstanding voltage characteristics of the cathode electrode and the gate electrode, thereby seriously deteriorating the driving stability of the light emission device.